Add Enumerable#group_by and Array#in_groups_of

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3726 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

2 files changed, 44 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/core_ext/array.rb b/activesupport/lib/active_support/core_ext/array.rb
index ddf2a369c1..897d73866c 100644
--- a/activesupport/lib/active_support/core_ext/array.rb
+++ b/activesupport/lib/active_support/core_ext/array.rb
@@ -2,4 +2,20 @@ require File.dirname(__FILE__) + '/array/conversions'
 
 class Array #:nodoc:
   include ActiveSupport::CoreExtensions::Array::Conversions
+
+  # Iterate over an array in groups of a certain size, padding any remaining 
+  # slots with specified value (<tt>nil</tt> by default).
+  # 
+  # E.g.
+  # 
+  #   %w(1 2 3 4 5 6 7).in_groups_of(3) {|g| p g}
+  #   ["1", "2", "3"]
+  #   ["4", "5", "6"]
+  #   ["7", nil, nil]
+  def in_groups_of(number, fill_with = nil, &block)
+    require 'enumerator'
+    collection = dup
+    collection << fill_with until collection.size.modulo(number).zero?
+    collection.each_slice(number, &block)
+  end
 end
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 49e1b7bb90..8a097dcd90 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -6,4 +6,31 @@ module Enumerable #:nodoc:
     end
     match
   end
-end
\ No newline at end of file
+
+  # Collect an enumerable into sets, grouped by the result of a block. Useful,
+  # for example, for grouping records by date.
+  #
+  # e.g. 
+  #
+  #   latest_transcripts.group_by(&:day).each do |day, transcripts| 
+  #     p "#{day} -> #{transcripts.map(&:class) * ', '}"
+  #   end
+  #   "2006-03-01 -> Transcript"
+  #   "2006-02-28 -> Transcript"
+  #   "2006-02-27 -> Transcript, Transcript"
+  #   "2006-02-26 -> Transcript, Transcript"
+  #   "2006-02-25 -> Transcript"
+  #   "2006-02-24 -> Transcript, Transcript"
+  #   "2006-02-23 -> Transcript"
+  def group_by
+    inject([]) do |groups, element|
+      value = yield(element)
+      if (last_group = groups.last) && last_group.first == value
+        last_group.last << element
+      else
+        groups << [value, [element]]
+      end
+      groups
+    end
+  end
+end